   // 广告图切换效果
   let xiao304 = document.querySelector('.xiao304'),
       banner = document.querySelector('.banner'),
       xiao302 = document.querySelector('.xiao302'),
       xiao306 = document.querySelector('.xiao306')
   console.log(banner)
   xiao304.onclick = function() {
       xiao304.classList.add("orange", "orangeColor")
       xiao302.classList.remove("orange", "orangeColor")
       xiao306.classList.remove("orange", "orangeColor")
       banner.style.backgroundImage = "url(/images/flash304.jpg)"
   }
   xiao302.onclick = function() {
       xiao302.classList.add("orange", "orangeColor")
       xiao304.classList.remove("orange", "orangeColor")
       xiao306.classList.remove("orange", "orangeColor")
       banner.style.backgroundImage = "url(/images/flash305.jpg)"
   }
   xiao306.onclick = function() {
       xiao306.classList.add("orange", "orangeColor")
       xiao302.classList.remove("orange", "orangeColor")
       xiao304.classList.remove("orange", "orangeColor")
       banner.style.backgroundImage = "url(/images/flash306.jpg)"
   }